EPA Method 200.8

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EPA Method 200.8:Determination of Trace Elements in Waters and Wastes by ICP-MS

Summary:Except for the determination of dissolved analytes aqueous samples are acid preserved prior to sample processing. For the analysis of dissolved analytes, an acidified portion the filtrate is analyzed directly. For the determination of total-recoverable analytes in aqueous samples containing particulate material as well as solid type samples, samples are subjected to acid pretreatment with nitric and hydrochloric acids and gentle refluxing prior to analysis. The method involves multi-element determination by inductively coupled plasma-mass spectrometry. Sample solutions are pneumatically nebulized into a radio-frequency plasma where ionization occurs. The ions are extracted from the plasma through a differentially pumped vacuum interface and separated on the basis of their mass-to-charge ratio by a quadruple mass spectrometer. Separated ions are detected by an electron multiplier or Faraday detector and the ion information processed by a data handling system. Isobaric and polyatomic interferences relating to the technique must be recognized and corrected. Instrument drift and matrix effects must be corrected with the use of internal standards.

Scope:This method determines 21 elements as dissolved elements in ground waters, surface waters, and drinking water, and total recoverable elements in these waters as well as wastewaters, sludges, and soils samples. Total-recoverable determination data should be reported as "total" (dissolved + suspended fractions) metal data. Organometalic compounds (such as arsenic compounds) are only determined as "total metals" and not as the individual organometalic compounds.

Citation:Methods for the Determination of Metals in Environmental Samples, Supplement 1 (EPA/600/R-94/111)

Interferences:(1) Isobaric elemental interferences caused by isotopes of different elements which form singly or doubly charged ions of the same nominal mass-to-charge ratio and cannot be resolved by the mass spectrometer in use.(2) Signals from relatively abundant isotopes can coalesce at the wings of relatively less abundant isotopes leading to loss of resolution and poorer quantitation.(3) Isobaric polyatomic ion interferences are caused by ions consisting of more than one atom with the same nominal charge-to-mass ratio of the isotope of interest.(4) Physical interferences that hinder transport of the sample into the plasma (e.g., viscosity effects, high levels of solids).(5) Memory interferences (carry-over) of isotopes from previous sample runs.

Concentration:The analytical range depends on the type of detector utilized (electron multiplier or Faraday cup) and extends from the laboratory determined MDL to the upper limit of the linear dynamic range.

Precision:Data (excluding that for mercury) was from joint EPA-AOAC 13-laboratory round robin validation. The precision and accuracy values presented are based on analyses of spiked reagent water samples. However, the method contains multilaboratory data and regression equations for metals analyses in drinking water, and ground water, and reagent water, as well supplemental single-laboratory data in a variety of matrices and media. NOTE: Mercury data was based on analyses of 3 drinking water samples fortified with mercury. One sample had background concentration above the MDL (0.23).

Detection:(1) Instrument detection limits (3-sigma) estimated from seven-replicate integrations of the blank (1% v/v nitric acid) following calibration of the instrument with three replicate integrations of a multi-element standard. (2) IDLs were estimated from single-laboratory, reagent water data.

Revision Number:Revision 5.4, 1994

Test Description:Trace Elements in Wa

Report Number:600/R-94-111

Date Issued:5/1/1994

Instrument used for this test:ICP-MS

At least 21 analytes can be tested by ALS - Columbia using EPA Method 200.8. Please contact us for all available analytes which can be tested by EPA Method 200.8.